The present invention relates to a layer-picking clamp supported on a truck for gripping at least one layer of items which form part of a layered load.
Warehouses commonly contain narrowly spaced rows of shelving designed to hold pallets of stacked goods, usually composed of stacked layers of cartons containing like items. Forklift trucks raise and lower entire pallets to and from the shelving. However, in certain cases only one or two layers from a particular pallet is needed, not the entire palletized load, particularly when preparing a palletized load of mixed layers of different items for shipment. Williams U.S. Pat. No. 4,252,496, Vasseur et al. U.S. Pat. No. 4,603,896, Richardson U.S. Pat. No. 5,161,934, Williams U.S. Pat. No. 5,253,974, and Tygard U.S. Pat. No. 5,516,255 are directed to clamping devices that may be used to grip a layer of items. These clamping devices are generally mounted on or incorporated with forklift trucks from which the forks have been removed.
Generally, to use the traditional devices, the forklift operator must first position the clamping portion above a layered pallet. Correct positioning requires skillful forklift maneuvering since the clamping portion can usually be positioned solely through correct positioning of the forklift. Once in the correct position, the clamping portion grips one or more layers of items. Then, the forklift can be used to raise the layer and carry it to a receiving pallet upon which the layer is deposited. By repeating this procedure, the operator collects different layers from different randomly located pallets and builds a load of mixed layers on the receiving pallet.
The Tygard device disclosed in U.S. Pat. No. 5,516,255 reduces the time wasted in positioning the forklift by allowing a side-mounted clamping device to shift sideways from a position close to the truck to a position further from the truck. Further, Tygard discloses that the design could be modified so that the side-mounted clamping portion, while to one side of the truck, could also be adjusted in the fore and aft direction of the truck. This limited motion allows an operator to compensate for misalignment of the truck without having to reposition the entire truck. The Tygard device, however, does not eliminate the time-consuming need to drive and reposition the truck between the place where a layer is picked up and the place where it is deposited on the receiving pallet.
Focke et al. U.S. Pat. No. 5,338,150 sets forth a stationary device that creates layers on a pallet by gripping one or two cartons and removing them from a conveyor, pivoting to a pallet, and arranging the cartons on the pallet. The gripper end of an articulated laterally swingable boom can pivot in a 180.degree. range for left or right-hand operation. However, this device has no mobility to enable it to collect layers from different random locations, and it is limited to gripping one or two cartons, not layers.
The foregoing devices use downwardly pivoting arms to grip the layer, which enable the gripping surfaces to engage the vertical sides of the layer in parallel relation thereto only in the case of a single set of horizontal layer dimensions. Other dimensions prevent such parallelism, and therefore prevent the gripping surfaces from imposing clamping force over the entire gripping surface, creating damaging force concentrations and poor gripping.
What is needed, then, is a layer-picking clamp that is integral with or mountable on a truck. Together, the clamp and truck should be versatile enough to reduce the need for time-consuming forklift driving and maneuvering. Layers of different horizontal dimensions should be engageable with equal effect.